1955 Ford Part 99: WOT (Wide Open Throttle) on the Holley Carburetor

WOT on the Holley

Over the Christmas holidays my son and I took some time to tinker in the garage. He bought a 1995 Ford Explorer earlier this year and had commenced installing a few Christmas presents in the vehicle (interior lighting, a touch-panel radio and back-up camera, and a few other odds and ends). While helping him grab some tools I decided to pop the hood on the Fairlane and do some tinkering of my own. With the 55 Ford in the garage on a very cold morning below freezing I closed the choke and hit the key. She turned over a couple of times but did not start of course. The hood happened to be up and I was actually standing at the driver's door so I hit the key again while giving the accelerator pedal a few pumps. For some reason I was looking at the engine through the open hood and watching the action of the carburetor linkage. SURPRISE! When I pushed the accelerator pedal to the floor a few times the carburetor butterflies were opening only half way!

"What gives here?" I questioned. After a brief examination of all moving parts I confirmed that there were no broken or missing pieces of hardware, everything was fastened securely, and none of the linkage had any play. Then it dawned on me... Ever since I had removed the Fordomatic and installed a 3 speed with overdrive, I had never really checked to see that my linkage was given me wide open throttle (WOT) when the accelerator pedal was pressed to the floor. The performance of the car had really improved, so much so that lighting up radial tires was a pretty easy accomplishment. (Not that the Hot Rod Reverend makes that standard practice - not so sure the transmission can handle it!) The throttle response was so good even with the Edelbrock, top end was so good, I just assumed that the installation and travel of the pedal all the way through to the carburetor was just fine. I guess I never had anyone sit in the driver's seat with the pedal to the floor so that I could check the full range of motion. Dummy me. I have had this thing up to 90 mph on the interstate and have always felt like she had more in her because the accelerator pedal was nowhere near floored, the carburetor very responsive, and the engine was just humming along. Not that I need to go any faster, but I would like to have things operating as they should concerning full travel on the carb butterflies.

At any rate, I have attached a photo of my linkage with the Edelbrock (the Holley is the same except for the rod itself) and some files of Ford's diagrams that will explain my setup. I have both of Ford's large parts manuals that show both the illustrations and the nomenclature. I have a 56 Ford 4 barrel Fordomatic accelerator assembly attached to a B intake. It looks very similar to this 57 model...

The difference in the 56/57 parts I believe would be how the Fordomatic kick down rod attaches. For 56 there is a pin that an L shaped bracket fastens and for 57 there is a hole to receive a clevis. At any rate, what I did was to retain this assembly but place a bolt/nut to stop in the slot (indicated by the red circle in the diagram and also by the yellow arrow in the photo) so that the assembly would be "locked" but continue to pivot and pull back the rod that attaches to the carb butterflies. Before I made this switch from auto to manual, this linkage was working just fine while attached to the original 55 pivot at the firewall. Just like the diagram at the beginning of this post.

This diagram below shows the "typical" 55/56 Ford Passenger Car setup with the Y block. Note that the part number 9725 is the same but the actual part itself is different in both the lower leg of the pivot and the attaching arm up top. Of course, the 4 barrel setup is not shown in the parts manuals for some reason so what is referenced below is for the 2 barrel (passenger side butterfly access) carburetor and intake manifold. One would assume that to be authentic I would need the 4 barrel linkage for the intake AND the correct firewall pivot.

I made a few inquiries on some well-traveled internet forums and it did not take long for responses. Within the first 24 hours, two fellas in particular offered up some extra parts they had in their inventory and I went ahead and bought an original firewall pivot. Because of some confusion in the messaging, I ended up purchasing two firewall pivots from different parties. No problem there - I decided to use the best one and sell the other. Here are the photos of what both individuals sent me. If you reference the diagram above and compare it to the first photo below, you will see that part number 9784 (the small stud and linkage rod) is attached to the long arm. I would assume that this pivot was for a manual car with the 2 barrel since 9784 is positioned to the passenger side of the car.

The two pictures below compare the two firewall pivot assemblies. The pivot for manual transmissions includes a flat piece of metal stock, while the unit for the Fordomatic does have a particular offset meant for use with the assembly that attaches to the intake manifold. If you examine the two diagrams above (straight from the Ford parts book) you would be led to beleiv that the orientation of the arm is the same between both pivots. Of course, a simple look at the photos below will let you know this is not the case - the Fordomatic's arm should be cocked more in a 60 degree angle down when compared to the manual version. With simple physics it is easy to understand why I was not getting full throttle - the "throw" or travel of the end of the arm was nowhere near the distance needed. Also, the orientation of the arm on the Fordomatic pivot would have never worked with a simple rod to the carburetor. While the video at the end of this post will show more specifics as to how tight this assembly is in mounting to the firewall, it is pretty easy to see that removing or installing this small hardware can be a challenge. Two sheet metal cap screws (3/8" heads) secure the pivot to the firewall, the small curved rod attaches to the rear of the accelerator pedal, and two small bolts with 1/2" heads hold the shaft bracket in place at the rear of the block. Magnetic sockets certainly help as would thin fingers!

The photo and edited text below explains some of the setup and adjustments that were made along with the nuances of particular parts. Thankfully, I had a carburetor linkage rod in one of my parts bins (well, actually 3 or 4) that I was able to modify concerning length and use with the existing other pieces of the linkage. After the linkage rod was cut to size, I did add about 3/4" more thread to along its length.

The rod pictured below was cut to length and more thread added for adjustment. I was reminded how helpful it is to keep parts and not discard items that you believe you may use one day. Obviously we will never use them all, but countless times I have visited my "stash" to help friends or work on my own vehicles.

Below is a video of the problem, the process, and the results... thanks to the fellas who were quick to offer up the manual transmission version of FoMoCo's firewall pivot assembly!

The Hot Rod Reverend

aka Daniel Jessup